Synthesis and characterization of metal-sulphur ligand complexes having high third-order optical nonlinearities

Synthesis and characterisation of metal-sulphur ligandcomplexes having high third-order optical nonlinearitiesCallum A S Hill, Allan E Underhill, Adam CharitonDepartment of Chemistry, University of Wales,Bangor, Gwynedd LL57 2UW, U.K.ABSTRACTMetal dithiolenes (Fig. 1) consist of conjugated organo sulphurligands bound to a central metal atom and exhibit a range of interestingelectrical and optical properties. Until recently this type of material wasprimarily of interest owing to the ability of some derivatives to act asu-electron donors in "organic metal" charge transfer salts1, though a resonantenhanced nonlinearity has been measured in the derivative BDN. 2 Electrondelocalisation involving interaction through the metal leads to materialshaving low energy excited states. Strong absorption bands can occur throughoutthe visible and near infra-red regions depending on the exact nature ofsubstitution. Tuning the absorption band near to the laser fundamental canresult in the observation of a high nonlinear refractive index (n2 =